Retailers can track shoppers in their store and retail locations via multiple modalities. One modality is to detect the presence of a mobile device carried by the shopper. Sensors deployed in the retail location can use signals from the mobile device to recognize the duration of the shopper's trip. A mobile device can also contain a unique identifier (such as a MAC address) that can be used determine when that mobile device (and therefore the shopper) returns to a retail location. While there is value in detecting the presence of a shopper in a retail location, there is a need to associate the presence (and trajectory) of a mobile device with the transaction data from the shopping trip.